Fibrous mat and method of manufacture



March 12, 1963 H. A. FOX

FIBROUS MAT AND METHOD OF MANUFACTURE 2 Sheets-Sheet 1 Filed Nov. 12, 1957 jMefJruqae A TTORNEYS March 12, 1963 H. A. FOX

FIBROUS MAT AND METHOD OF MANUFACTURE mm W 2 Sheets-Sheet 2 A TTORNE YS Filed Nov. 12, 1957 United States Patent 3,081,207 FIBROUS MAT AND METHOD OF MANUFACTURE Herbert A. Fox, Perrysburg, Ohio, assignor, by mesne assignmeuts, to JohnsManville Fiber Glass Inc., Cleveland, Ohio, a corporation of Delaware Filed Nov. 12, 1957, Ser. No. 695,652 Claims. (Cl. 154-44) This invention relates broadly to the manufacture of fibrous mats, and more particularly to new and improved mats utilizing mixtures of glass fibers.

This application is a continuation-in-part of my copending application Serial No. 475,514, filed December 15, 1954, now abandoned.

It is a primary object of the present invention to provide non-woven fibrous mats having high tear strength, high resiliency and excellent thermal properties.

Another object of the invention lies in the provision of a method of producing mats of the above character, wherein bundles of relatively coarse glass fibers are combined with relatively fine staple glass fibers to produce integrated products.

Other objects and advantages of the invention will become more apparent during the course of the following description when taken in connection with the accompanying drawings.

In the drawings, wherein like numerals are employed to designate like parts throughout the same:

FIG. 1 is a perspective view of an apparatus suitable for forming fibrous mats of the character herein de scribed;

FIG. 2 is a perspective view of a small piece of a fibrous mat of this invention illustrating a typical arrangement of fibers; and

FIG. 3 is an enlarged view of the surface of the mat of FIG. 2.

Although the invention is not restricted to the production of fibrous mats from any particular material, it is especialy well adapted to the manufacture of such mats by utilizing mixtures of glass fibers and will be described in that connection.

With reference now to the drawing, there is illustrated an apparatus suitable for making mats of a type contemplated by the invention and includes a unit for forming fine glass fibers and a mill 11 for shredding continuous glass strand to be added to the first fibers.

The glass fiber forming unit 10 includes a feeder 12 for feeding a plurality of streams of molten glass 13, which are formed into glass rods 14 by coacting rollers 15 and 16 driven by any suitable means.

The rods 14 after emerging from between the rollers 15 and 16 are fed past a port 17 in a burner 18 and into a high speed gaseous blast emanating from said port. The blast is intensely hot so that as the rods 14 move into the blast they are melted and the molten glass is attenuated by force of the blast into fine glass fibers a. This blast is preferably formed by a burner which utilizes a combustible gaseous mixture, for instance a mixture of fuel gas, either natural or manufactured, and air.

As the attenuated fibers a are deflected and entrained by the gaseous blast, they are borne past nozzles 19 which spray the fibers with a coating of an adhesive or binder material 20. This binder or adhesive may be of any of the well known types such as a dilute water solution or suspension of boiled tapioca flour, starches, dextrines, glues, resinous suspensions or solutions such as polyvinyl alcohol, methyl cellulose, melamine formaldehyde, urea formaldehyde, phenol formaldehyde, latex and others.

After the fine fibers a have been carried past the nozzles 19, they are deposited upon a suitable collecting means such as an endless conveyor. One such apparatus for 3,081,207 Patented Mar. 12, 1963 collecting the fibers includes an air porous, endless conveyor belt 21, suitably fabricated of woven wire screen, through which the products of combustion are induced to flow by means of suction. The porous belt 21 retains the fibers and allows the gaseous products to be dissipated to the atmosphere. By so operating a mat 22 of random fibers is built up on the belt 21.

The size of the fibers a, attenuated by the gaseous blast may be varied in several ways known to those skilled in the art of manufacture of such fibers. For example, the speed of the rolls 15 and 16 can be increased, conditions of feeder 12 remaining constant, thereby reducing the diameters of the rods 14. The result wiil be that the fibers a are of smaller diameter and shorter length. Conversely by reducing the speed of rolls 15 and 16 the diameters of the rods 14 will be increased with corresponding increase in coarseness of the fibers a. It will be apparent that by varying the size of the attenuated fibers a, the characteristics of the mat formed therefrom may be altered to varying degrees to produce end products of selected properties. Generally fibers of larger diameter produce mats of greater resiliency and lower insulating value whereas fibers of smaller diameter produce mats of lesser resiliency and higher insulating value.

According to one aspect of the present invention, the attenuated fibers a are admixed with shredded glass strand, the specific mixture of fibers employed being determined by the qualities desired in the end product. The shredded fibers b are uniformly deposited upon the attenuated fibers a, carried by the conveyor belt'21, in the following manner:

Continuous glass strand is first formed into portions adapted to convenient handling which are then placed in a primary hopper 23 and fed by an anger conveyor 24 to the inlet 25 of the shredding mill 11. In the mill the shredding action is effective to break up the continuous strand into random lengths of pantially dispersed bundles of fibers. -By means of a centrifugal blower 26, attached to the outlet of mill 11, the shredded strand is blown onto conveyor belt 21 and deposited upon the previously formed mat of fiber a. Blower 26 has a hollow duct 27, suitably of circular configuration, attached to its exhaust port 28 which extends to a discharge position adjacent the left-handend of conveyor belt 21. Duct 27 is provided at its free end with a flexible tube member 29, of

- spread material expelled therefrom.

A gear box (not shown), suitably connected either to the power means for driving the shredding mill 11 or centrifugal blower 26 is provided with an upstanding drive shaft 31. A horizontally disposed eccentric plate 3 2 is secured on the upper end of shaft 31 and a U-shaped yoke member 33 is secured around the free end of flexible conduit 29 at the base of the nozzle 30. A counectingrod 34 having one of its ends pivotally connected to the yoke 33 and its other end pivotally connected to the eccentric plate 32 provides a driving connection whereby the nozzle 30 is moved to and fro in an arcuate manner to direct the shredded fibers b in a uniform manner across the continuous belt 21. Nozzle 30 is slidably supported upon an arcuate plate 35, carried by an inverted, U-shaped support 36 which is positioned over the conveyor belt 21.

When the shredded fibers b make contact with the coated fibers a, they tend to blend with the coated fibers and become partially coated with the binder material that has been placed on the fibers a. If desired, additional binder may be sprayed upon the composite mat as the shredded fibers are applied to thereby provide increased bonding. The mat 22 thus formed has high tear strength and considerable resiliency because of the interlacing and interbonding of the high strength textile fibers b and the attenuated fibers a. It will be apparent that the characteristics of the fibrous mat formed may be changed by increasing or decreasing the ratio of shredded fibers b, added to the attenuated fibers :1. These ratios may be changed by changing the speed at which the glass rods 14 are drawn from the feeder 12, the velocity and temperature of the gas blasts from the burner 18, the speed at which the shredded fibers are discharged from the nozzle 30 and also by varying the forward speed of the conveyor belt 21.

After the mat 22 has been formed on the conveyor belt 21, it may be carried to further treating stations such as forming rollers (not shown) to press the mat to uniform thickness, and then to an oven 37 where the binder is activated to set the mat in a desired shape. As it is best shown in FIGS. 2 and 3, the resulting mat is a composite structure comprised of short staple glass fibers and random lengths of partially dispersed. bundles of fibers of larger diameter.

As an alternate procedure, the mat 22.may be further impregnated with other types of resins, instead of the rolling and oven treatment. In this connection, the mat may be further impregnated with a thermosetting phenol formaldehyde resin and may be laminated and pressed to a desired shape and configuration or, it may be impregmated with a resin which is only slightly activated thus allowing the mat to be formed and set at a later date.

While the invention has been described in its principal embodiment as employing shredded glass strand, it is not the intent to limit the concept thereto. Thus other glass fibers may also be employed separately or in admixture with the glass strand. For example, so-called staple glass fibers may be used. These may be of largeror smaller diameter than the attenuated fibers a. Such staple fibers may be either preformed virgin fibers or scrap fibers such as trim from the production of glasswool insulating mats wherein the fibers are bonded together at their points of contact by a material such as a thermosetting phenolformaldehyde resin.

It is also to be considered within the scope of this invention to position the nozzle 36 at a point analogous to one of the nozzles 19. By so operating the shredded fibers b will be intermixed all through the thickness of the mat 22, rather than being deposited in a uniform manner on the surface thereof.

It is also to be considered within the scope of the present invention to form mats employing the shredding mill 11 exclusively. When so operating, previously manufactured fibers are fed through the mill 11. .For example, combinations of glass textile fibers, very fine flame attenuated fibers and/or coarser glass wool fibers may be used. Thus they are simultaneously shredded and admixed and are then directed upon the belt 21. As described above, resin can be applied to the admixed fibers while they are airborne, i.e., with the nozzles 19 directed ahead of nozzle 30.

The mats produced by the present invention are adapted to a variety of uses. For example a mat having a high ratio of the fine attenuated fibers a provides an excellent thermal insulating material for homes, factories and the like. Also the material can be employed to wrap heating ducts, steam lines, refrigeration lines, or others to reduce heat transfer. When the ratio of glass textile fibers b is increased, the mat formed will be of a higher strength and is thus adapted for use as a reinforcement for synthetic resins for the production of various shaped and molded parts and others.

It is to be understood that various modifications may be made in the composition and procedure herein disclosed without departure from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. A fibrous glass mat comprising a first layer of short staple glass fibers of unequal length, a second layer of random lengths of partially dispersed bundles of glass fibers of larger diameter, said bundles of fibers having lengths greater than the staple fibers, said first and second layers being interfelted and interbonded at their contiguous faces and all of the fibers being bonded together at their points of contact to form a stabilized mass.

2. A method of forming a fibrous mat, comprising severing glass fibers into sections, conveying the severed sections in an air stream toward a collecting surface against which the air-borne fibers are to be directed to be collected into mat form and upon which has been deposited glass'fibers of a lesser diameter and shorter length than said air-borne fibers and which fibers are in the process of being formed into a first mat, said air stream having a width less than the Width of the collect ing surface, and reciprocating the air stream to and fro .in' an arcuate path transversely relative to the collecting surface while directing the air stream toward said collecting surface depositing fibers thereon as a substantially uniform layer and interlacing said fibers into the contiguous surface of said first mat being formed.

3. A method as defined in claim 2, wherein a binder is applied to the air-borne fibers prior to said fibers being formed into a mat.

4. A method of forming a mat as defined in claim 2, wherein a first mat is formed on the collecting surface by directing a gaseous blast containing individual fibers through said collecting surface while adding a binder to the individual fibers, subsequently depositing the airborne stream of fibers on the mat of individual fibers and interlacing said air-blown fibers within the contiguous surface of said mat, adding additional binder simultaneously with the deposition of the air-borne fibers, and then activating the binder to bond the fibers to one another.

5. A method of forming a multi-layer fibrous mat, comprising collecting a first layer of binder impregnated individual glass fibers upon a moving collecting surface to form a first mat, advancing said mat while being formed a predetermined distance, depositing a substantially uniform layer of strand glass fibers on the first mat while said first mat is being formed, said strand glass fibers having an average diameter greater than the average diameter of the fibers of the first mat, wherein the strand glass fibers are carried in an air stream prior to being deposited, and the air stream is reciprocated transversely relative to the collecting surface to substantially uniformly deposit the strand glass fibers on the first mat and interlace the strand glass fibers within the contiguous surface of said mat, and activating the binder to bind the fibersin the first mat to one another and the fibers in the second mat to said first mat.

References Cited in the file of this patent UNITED STATES PATENTS 2,477,555 Roberts et al July 26, 1949 2,604,427 Armstrong et al. July 22, 1952 2,639,759 Sirnison May 26, 1953 2,719,336 Stotler Oct. 4, 1955 2,728,699 Labino Dec. 27, 1955 2,731,066 Hogendobler et al Jan. 17, 1956 2,746,096 Baxter et al May 22, 1956 2,751,962 Drummond June 26, 1956 2,765,247 Graham Oct. 2, 1956 

1. A FIBROUS GLASS MAT COMPRISING A FIRST LAYER OF SHORT STAPLE GLASS FIBERS OF UNEQUAL LENGTH, A SECOND LAYER OF RANDOM LENGTHS OF PARTIALLY DISPERSED BUNDLES OF GLASS FIBERS OF LARGER DIAMETER, SAID BUNDLES OF FIBERS HAVING LENGTHS GREATER THAN THE STAPLE FIBERS, SAID FIRST AND SECOND LAYERS BEING INTERFERED AND INTERBONDED AT THEIR CONTIGUOUS FACES AND ALL OF THE FIBERS BEING BONDED TOGETHER AT THEIR POINTS OF CONTACT TO FORM A STABILIZED MASS. 